From: Waiman Long <longman@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will.deacon@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Tim Chen <tim.c.chen@linux.intel.com>,
huang ying <huang.ying.caritas@gmail.com>
Subject: Re: [PATCH-tip v7 00/20] locking/rwsem: Rwsem rearchitecture part 2
Date: Sun, 28 Apr 2019 20:27:54 -0400 [thread overview]
Message-ID: <604c8751-5269-de29-0b7f-b3e93b6df4ca@redhat.com> (raw)
In-Reply-To: <CAHk-=wg_facR6y3gnmtGwBSJYZdHm5rWSPpPhJG6XswW4+mO1Q@mail.gmail.com>
On 4/28/19 8:10 PM, Linus Torvalds wrote:
> On Sun, Apr 28, 2019 at 4:12 PM Waiman Long <longman@redhat.com> wrote:
>> I implemented your suggestion in patch 1 as it will produce simpler and
>> faster code. However, one of the changes in my patchset is to wake up
>> all the readers in the wait list. This means I have to jump over the
>> writers and wake up the readers behind them as well. See patch 11 for
>> details. As a result, I have to revert back to use list_add_tail() and
>> list_for_each_entry_safe() for the first pass. That is why the diff for
>> the whole patchset is just the below change. It is done on purpose, not
>> an omission.
> Ahh, ok. In that case I suspect the clever code isn't even worth it,
> since it very much depends on just splitting the list in a fixed
> place.
>
> Linus
Not really, this is a serious problem that have to be backported to
earlier stable releases and downstream. The clever code is helpful in
those cases.
Cheers,
Longman
next prev parent reply other threads:[~2019-04-29 0:27 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-28 21:25 [PATCH-tip v7 00/20] locking/rwsem: Rwsem rearchitecture part 2 Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 01/20] locking/rwsem: Prevent decrement of reader count before increment Waiman Long
2019-05-03 12:06 ` Peter Zijlstra
2019-05-03 13:32 ` Waiman Long
2019-05-07 7:07 ` [tip:locking/urgent] " tip-bot for Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 02/20] locking/rwsem: Make owner available even if !CONFIG_RWSEM_SPIN_ON_OWNER Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 03/20] locking/rwsem: Remove rwsem_wake() wakeup optimization Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 04/20] locking/rwsem: Implement a new locking scheme Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 05/20] locking/rwsem: Merge rwsem.h and rwsem-xadd.c into rwsem.c Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 06/20] locking/rwsem: Code cleanup after files merging Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 07/20] locking/rwsem: Make rwsem_spin_on_owner() return owner state Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 08/20] locking/rwsem: Implement lock handoff to prevent lock starvation Waiman Long
2019-05-03 13:10 ` Peter Zijlstra
2019-05-03 13:57 ` Waiman Long
2019-05-03 14:37 ` David Laight
2019-04-28 21:25 ` [PATCH-tip v7 09/20] locking/rwsem: Always release wait_lock before waking up tasks Waiman Long
2019-05-03 13:37 ` Peter Zijlstra
2019-05-03 13:56 ` Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 10/20] locking/rwsem: More optimal RT task handling of null owner Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 11/20] locking/rwsem: Wake up almost all readers in wait queue Waiman Long
2019-05-03 16:51 ` Peter Zijlstra
2019-05-03 17:15 ` Waiman Long
2019-05-06 11:49 ` Peter Zijlstra
2019-04-28 21:25 ` [PATCH-tip v7 12/20] locking/rwsem: Clarify usage of owner's nonspinaable bit Waiman Long
2019-05-03 15:21 ` Peter Zijlstra
2019-05-03 15:26 ` Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 13/20] locking/rwsem: Enable readers spinning on writer Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 14/20] locking/rwsem: Enable time-based spinning on reader-owned rwsem Waiman Long
2019-05-06 15:47 ` Peter Zijlstra
2019-04-28 21:25 ` [PATCH-tip v7 15/20] locking/rwsem: Adaptive disabling of reader optimistic spinning Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 16/20] locking/rwsem: Add more rwsem owner access helpers Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 17/20] locking/rwsem: Guard against making count negative Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 18/20] locking/rwsem: Merge owner into count on x86-64 Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 19/20] locking/rwsem: Remove redundant computation of writer lock word Waiman Long
2019-04-28 21:25 ` [PATCH-tip v7 20/20] locking/rwsem: Disable preemption in down_read*() if owner in count Waiman Long
2019-04-28 22:46 ` [PATCH-tip v7 00/20] locking/rwsem: Rwsem rearchitecture part 2 Linus Torvalds
2019-04-28 23:12 ` Waiman Long
2019-04-28 23:19 ` Waiman Long
2019-04-29 0:10 ` Linus Torvalds
2019-04-29 0:27 ` Waiman Long [this message]
2019-04-29 2:41 ` Linus Torvalds
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